Force transfer devices, which are disposed between a drive engine and a transmission unit, are known in a plurality of embodiments in the state of the art. They typically comprise an input and at least one output, wherein the input can be coupled at least indirectly, this means, directly or through further transfer elements, with a drive engine, typically an internal combustion engine, and at least one output, which is coupled with a transmission unit, which is disposed subsequent to the force transfer device, typically a change speed transmission. Between the input and the output, a hydrodynamic component, preferably in the form of a hydrodynamic speed-/torque converter, is disposed. It comprises at least a pump shell and a turbine shell and at least one stator shell. For bridging the hydrodynamic power transfer, a device is provided, which is also designated as a lockup clutch. It comprises a first clutch component and a second clutch component, which can be brought into operative engagement, at least indirectly. The lockup clutch is thus used for coupling between the input, or the connection between the input and the pump shell and the turbine shell. The activation or deactivation is performed through an actuation device, which is provided in the simplest case in the form of a piston element, which can be actuated through a pressure medium. Depending on the embodiment, the hydrodynamic speed-/torque converter or the entire force transfer device is provided as a two- or three-channel unit. When provided in three-channel construction, thus the actuation device for the lockup clutch is loaded with a pressure, which is separately adjustable. The hydrodynamic speed/torque converter is flowed through in a centripetal or centrifugal manner, depending on the conditions in the connections associated with the operating volume and the internal cavity enclosed by the housing and the hydrodynamic speed/torque converter. Depending on the coupling of the connections with a pressure medium supply system, a loop, which is, however, external with reference to the flow loop, established in the hydrodynamic speed/torque converter during operation, can be created. Thus, the power is transferred purely hydro-dynamically in an operating range through the power flow between the input and the output occurring through the hydrodynamic component. The primary shell, operating as pump shell, is coupled directly with the drive engine, and the turbine shell is coupled with the output or the input of the subsequent change speed transmission. In order to avoid the disadvantages of hydrodynamic power transmission in vehicle applications, which occur in the operating map of the drive engine at the required higher speed/torque settings, in order to avoid a systematic slippage of 2-3% and closing the operating map, the lockup clutch is activated and the power is transferred between the input and the output of the force transfer device, mechanically circumventing the hydrodynamic power path.
In combination with hybrid drives, in which the braking action is preferably performed electrically, and in which the braking energy is stored, when using an electric motor as a generator, a residual moment is still transferred into the transmission, or slipped into the drive engine, during braking operation, when the lockup clutch is open, when the electric motor is disposed in the transmission or in front of it, but behind the force transfer device, so that the full braking energy cannot be stored as electrical energy.
Furthermore, the drive engine can be separated from the output through opening the lockup clutch; however, torque is still transferred into the hydrodynamic component, which is transferred again into the subsequent transmission due to the coupling. On the other hand, torque peeks from the output are transferred into the hydrodynamic components. For decoupling the drive engine from the transmission, thus either an idle cutoff is provided in the transmission, this means, interruption of the force flow in the transmission at idle, or a coupling device is provided, which is used for decoupling the pump shell, and thus for decoupling the drive engine from a transmission unit, disposed subsequent to the force transfer device, as described in U.S. Pat. No. 5,020,646. The pump shell coupling is thus only required for this operating range. It is often also disposed in a range, which then leads to the enlargement of the required installation volume in radial or axial direction. Due to the possibility to separate between the pump shell and the drive engine, typically between the pump shell and the input of the force transfer device, a housing is provided, enclosing the entire unit, in particular also the pump shell. The hydrodynamic component however remains functionally associated with the transmission unit, when the pump shell is decoupled, this means, coupled with said transmission unit, which creates slip losses, in particular during separation in coasting operation. An idle cutoff in the transmission interrupts the force flow, however, the hydrodynamic component is still coupled with the drive engine, so that a moment is transmitted into the transmission, at least up to the separation location, which causes slippage losses.